With an increasing demand for smaller outline consumer electronic products, electronics manufacturers are in turn seeking to minimize the size of components. An example of this is the move from plated through hole components to surface mount components in circuit board assembly.
Integrated circuit manufacturers are not immune from these demands with pitch sizes continually decreasing. A result of this is the introduction of Chip Scale Packages (CSPs). Chip scale packages are generally considered to be packages where the overall footprint (board area occupied) of the package is within 30% of the actual chip size. Wafer Level Chip Scale Packages (WLCSPs) are a type of CSP in which the traditional wire bonding arrangements are dispensed with in favor of making direct contact by means of conductive bumps (typically solder balls) to the integrated circuitry. WLCSPs differ from fine pitch Ball Grid Array (BGA) and leadframe based Chip Scale Packages (CSPs) in that most of the packaging process steps are performed at wafer level.
The smaller form factor package size of WLCSP and their ability to be used with conventional surface mount assembly and reflow techniques makes them a popular choice where minimum board area/weight and package height are key requirements.
As such, WLCSP is gaining rapid acceptance as the package of choice for Radio Frequency (RF)/Analog, Power Management and other devices used in handheld and portable products where size is critical.
One problem with WLCSP parts is that they have exposed bare silicon that has been thinned (in that the typical WLCSP “package” thickness is significantly less than that of a typical fully encapsulated part) which (if mishandled or exposed to a non-optimized board assembly process) may be more susceptible to mechanical damage than a fully encapsulated part.
Whilst, there is a general requirement to reduce the space occupied by packaged integrated circuits in parallel with the general reduction in size\compactness of handheld electronic products, there is still a need to maintain reliability. The present application is directed at improving reliability with reduced package sizes.